The effects of an inhaled bronchodilator on the distribution of inspired gas and overall efficiency of ventilation were studied by the nitrogen washout technique in 16 patients with chronic obstructive pulmonary disease; 3 normal subjects and 2 patients with asymptomatic asthma (and normal spirometric values) were also studied. The response of anatomic dead space and/or pulmonary resistance to the bronchodilator was measured in 17 subjects and compared with the behavior of gas distribution and ventilatory efficiency. The effects of orciprenaline on nitrogen clearance were related to the degree of functional impairment. In normal and asthmatic subjects and in patients with chronic obstructive pulmonary disease and mild to moderate functional impairment, the nitrogen clearance did not vary significantly or showed changes suggesting less uniform gas distribution and reduced ventilatory efficiency. In most patients with severe chronic obstructive pulmonary disease the bronchodilator caused changes suggesting more uniform distribution of inspired gas and increased efficiency of ventilation. Multiple regression analysis showed that the behavior of the nitrogen clearance following bronchodilator treatment was also related to the response of the anatomic dead space. No relationship was found between the changes in nitrogen clearance and those in pulmonary resistance. The effect of orciprenaline on gas distribution and efficiency of ventilation was found to vary with time, the whole duration of the response being at least 1 to 2 hours. In 2 subjects, the inhalation of distilled water or saline solution caused changes in the nitrogen clearance suggesting more uneven gas distribution. The present results are consistent with the assumption that the changes in nitrogen clearance following bronchodilator treatment reflect the concourse of multiple factors, which may be expected to have favorable or unfavorable effects on the distribution of inspired gas and the efficiency of ventilation.
|Translated title of the contribution||Gas distribution and ventilatory efficiency in patients with chronic obstructive pulmonary disease, after inhalation of a bronchodilator|
|Number of pages||18|
|Journal||Policlinico - Sezione Medica|
|Publication status||Published - 1978|
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